Page 1 of 40

Internal Dosimetry Coworker Intake 

and Exposure Model for the W. R. Grace 

Company, Erwin, Tennessee

White Paper

National Institute for Occupational 

Safety and Health

March 1, 2019

Matthew G. Arno and Karen S. Kent 

Oak Ridge Associated Universities Team

Thomas P. Tomes 

Division of Compensation Analysis and Support 

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 2 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

TABLE OF CONTENTS

INTRODUCTION .......................................................................................................................... 6

PURPOSE....................................................................................................................................... 6

BACKGROUND ............................................................................................................................ 7

BIOASSAY DATA ...................................................................................................................... 10

COWORKER INTAKE RATES BASED ON BIOASSAY (1965-1973) ................................... 11

EXPOSURE MODEL TO DEVELOP PLUTONIUM INTAKE RATES BASED ON 

AIRBORNE CONCENTRATION DATA (1976-1993) .......................................................... 12

ORAUT-OTIB-0070 METHOD TO DEVELOP PLUTONIUM INTAKE RATES 

(1974-1975) .............................................................................................................................. 12

REFERENCES ............................................................................................................................. 14

Attachment A, Plutonium Coworker Statistical Analysis Methods.............................................. 17

Bioassay Data ........................................................................................................................... 17

Analysis .................................................................................................................................... 17

Intake Modeling........................................................................................................................ 17

Intake Assignment .................................................................................................................... 18

Plutonium Statistical Analysis Results..................................................................................... 20

Attachment B, Plutonium Coworker Statistical Analysis Instructions......................................... 28

Data Sources: ............................................................................................................................ 28

Instructions ................................................................................................................................ 28

Attachment C, Exposure Model To Develop Plutonium Intakes Based on Airborne 

Concentration Data ................................................................................................................... 30

Methods .................................................................................................................................... 30

Airborne Concentration Data .................................................................................................... 30

Analysis .................................................................................................................................... 32

Intake Modeling and Assessment ............................................................................................. 33

Attachment D, Plutonium Bioassay Program Review.................................................................. 36

1965 through 1973—Plutonium Production Period ................................................................. 36

1974 through 1989—Post-Production Period ........................................................................... 37

1990 through 1993—Plutonium Facility D&D ........................................................................ 40
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 3 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Tables

Table 1. Timeline of plutonium activities at W. R. Grace............................................................. 7

Table 2. Plutonium activity processed by project at W. R. Grace. ................................................ 8

Table 3. Summary of plutonium processes at W. R. Grace. .......................................................... 8

Table 4. Default plutonium assumptions, SEFOR MOX. ........................................................... 10

Table 5. Plutonium intake rates based on bioassay (Type M) (dpm/d). ...................................... 11

Table 6. Plutonium intake rates based on bioassay (Type S) (dpm/d)......................................... 11

Table 7. Total alpha intake rates based on airborne concentration data (dpm/d). ....................... 12

Table 8. Plutonium intake rates (Type M) (dpm/d). .................................................................... 13

Table 9. Plutonium intake rates (Type S) (dpm/d). ..................................................................... 13

Table A-1. 50th and 84th percentile urinary excretion rates of plutonium gross alpha, 

1967 to 1973 (dpm/d). .............................................................................................................. 18

Table A-2. Type M plutonium gross alpha intake rates (dpm/d). ................................................ 19

Table A-3. Type S plutonium gross alpha intake rates (dpm/d). ................................................. 19

Table C-1. Determination of plutonium vs. uranium areas. ........................................................ 31

Table C-2. Plutonium gross alpha air concentration results (1976 to 1993). .............................. 32

Table C-3. 50th--percentile plutonium intake rates (dpm/d). ...................................................... 33

Table D-1: Plutonium bioassay data in NOCTS 1974 through 1989. ......................................... 38

Figures

Figure A-1. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1967 to 1968, Type M .............................................................. 20

Figure A-2. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1969 to 1971, Type M ............................................................... 20

Figure A-3. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1972 to 1973, Type M ............................................................... 21

Figure A-4. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1967 to 1968, Type M ............................................................... 21
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 4 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Figure A-5. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1969 to 1971, Type M............................................................... 22

Figure A-6. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1972 to 1973, Type M............................................................... 22

Figure A-7. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, all years, Type M....................................................................... 23

Figure A-8. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, all years, Type M....................................................................... 23

Figure A-9. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1967 to 1968, Type S. ............................................................... 24

Figure A-10. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1969 to 1971, Type S. ............................................................... 24

Figure A-11. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, 1972 to 1973, Type S. ............................................................... 25

Figure A-12. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1967 to 1968, Type S. ............................................................... 25

Figure A-13. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1969 to 1971, Type S. ............................................................... 26

Figure A-14. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, 1972 to 1973, Type S. ............................................................... 26

Figure A-15. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 50th percentile, all years, Type S........................................................................ 27

Figure A-16. Predicted plutonium gross alpha bioassay results calculated using IMBAderived plutonium gross alpha intake rates (line) compared with measured bioassay 

results (dots), 84th percentile, all years, Type S........................................................................ 27

Figure C-1. Observed 1976-1987 fraction of plutonium MPC versus the standard normal 

quantiles (censored data do not appear on the plot).................................................................. 34
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 5 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure C-2. Observed 1988-1993 fraction of plutonium MPC versus the standard normal 

quantiles (censored data do not appear on the plot) .................................................................. 35
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 6 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

INTRODUCTION

A review by Sanford Cohen and Associates (SC&A) and Salient of the W. R. Grace, Erwin, 

Tennessee, site profile (ORAUT 2011) in February 2013 resulted in several findings, of which 

Finding 3 is associated with intakes of plutonium. SC&A noted the need for intakes for 

unmonitored workers and questioned why intakes of plutonium were not considered in dose 

reconstructions during the residual contamination period (SC&A and Salient 2013). 

W. R. Grace was an Atomic Weapons Employer (AWE) facility from 1958 through 1970 with a 

residual contamination period from 1971 through March 1, 2011 (DOE 2017). The current site 

profile (ORAUT 2011) provides instructions to reconstruct plutonium intakes for workers with 

plutonium bioassay data during the AWE contract period. The site profile does not provide 

plutonium intakes for individuals with no internal monitoring results. In addition, the site profile 

states that plutonium intakes are not reconstructed for the residual contamination period. 

The National Institute for Occupational Safety and Health (NIOSH) has reviewed the use of 

plutonium at W. R. Grace and now presumes dose from intakes of plutonium is covered under 

the Energy Employees Occupational Illness Compensation Program Act of 2000 (EEOICPA) in 

both the AWE operational and residual periods. 

PURPOSE

Some employees were not monitored for potential intakes of plutonium, or the records of such 

monitoring are incomplete or unavailable. In such cases, data from monitored coworkers was 

used to develop intake rates to address potential internal exposures of radioactive material during 

operations. This white paper provides plutonium coworker intake rates for the period of 

plutonium production at the site. These intake rates may be used to fill in gaps in internal 

monitoring data or used for workers presumed to have been exposed but not monitored for 

intakes of plutonium. In addition, alpha airborne concentration results from plutonium areas 

were used to develop plutonium intake rates for the post-operations period. 

The plutonium facilities were shut down in 1973. Decontamination and decommissioning 

(D&D) of the facilities occurred from 1990 through 1993. Individual bioassay data is presumed 

sufficient for all workers exposed to plutonium during the D&D period. This paper provides 

intake rates for 1974 through 1989 based on general area air sampling data; those intake rates are 

for incidental exposure to plutonium contamination for workers who entered the building but 

were not monitored for plutonium. Some workers were monitored for plutonium exposure 

during this period, and they are presumed to have been exposed to potentially higher levels of 

plutonium. A discussion of the plutonium bioassay program is provided in Attachment D. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 7 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

BACKGROUND

A summary of plutonium activities at W. R. Grace is shown in Table 1. 

Table 1. Timeline of plutonium activities at W. R. Grace. 

Timeframe Activity Reference

1964-1965

Plutonium facilities were constructed in Buildings 110 and 234. This 

was also known as the Mixed Oxide (MOX) UO2/PuO2 fuel 

fabrication facility. 

NFS 1988, ca. 2000; 

EG&G 1994

Late 1960s Additional plutonium facilities added for plutonium scrap dissolution. EG&G 1994, PDF p. 389

1965-1972 Operation of the MOX facilities (Buildings 110 Lab and 234), 

Fabrication of MOX fuel elements discontinued in 1972. 

NFS 1994; NRC 1991, 

PDF p. 27; Higinbotham 

1994, PDF p .4 

1973 MOX facility placed in safe standby. Haskins 1995; 

EG&G 1994

1973-1985 Nuclear Fuel Services (NFS) unsuccessful in finding a disposal site for 

wastes that would be generated from decommissioning activities. NFS 1988

04/1986 Contract signed which allowed NFS to ship transuranic (TRU) waste 

to U.S. Department of Energy (DOE)-Idaho Falls. NFS 1988

06/1988-

09/1988 MOX facilities were characterized. NFS 1994

01/1989-

07/1989 MOX facility safety systems upgrades/prepare for decommissioning. NFS 1994

06/20/1989 U.S. Nuclear Regulatory Commission (NRC) approval of 

decommissioning plan. 

NFS 1994; 

NFS and EkoTec 1990

06/28/1990 Completed Decontamination and Volume Reduction Facility and

started cold testing. NFS 1994

09/12/1990 MOX facility D&D began. NFS 1994

1991 Building 110 preparation for final release. NFS 1991

06/1993-

09/1993

Excavation of ~2,310 ft3 TRU contaminated soil from under Area B of 

Building 234 (Wet Chem Cell) w/~1700 ft3 remaining. NFS 1994

10/1993-

12/1993

Final cleanup of facilities; contaminated soils under the Wet Cell 

remained for future decommissioning. NFS 1994

As of 2009

Contaminated material remains (as of 2009) in the soil underground 

where the Building 234 Wet Cell used to exist. A large tent was 

placed over the building site.

NFS 2009

Plutonium operations began in 1965 and were permanently shut down in 1973 when the uranium 

oxide/plutonium oxide MOX fuel fabrication facility was placed into safe standby (Haskins 

1995). Between 1965 and 1973, approximately 812 kg of plutonium were processed for 

essentially four customers, as shown in Tables 2 and 3. Table 2 illustrates the plutonium activity 

processed by project. Table 3 provides a listing of job orders involving plutonium. The largest 

order covered the manufacture of about 2,000 PuO2-UO2 MOX fuel rods for the Southwest 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 8 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Experimental Fast Oxide Reactor (SEFOR). This was a joint undertaking of General Electric 

(GE), the U.S. Atomic Energy Commission (AEC), and several utility companies. The GESEFOR order and the DuPont/Savannah River Operations Office (SROO) order comprised 94% 

of the plutonium introduced to the facility (NFS 1988). 

Table 2. Plutonium activity processed by project at W. R. Grace. 

Project Original kg Pu Ci/g TRU Total Curies

SEFOR 762a 0.648 493,776

Halden 3 3.610 10,830

Consumers 23.5 1.470 34,545

West Valley 23.5 2.800 65,800

Total 812.0 Not applicable 604,951

Source: NFS 1988. 

Note: Isotopes present: 238Pu, 239Pu, 240Pu, 241Pu, 242Pu and 241Am.

a. Includes 16 kg of plutonium used on the DuPont project for which no isotopic data 

is available.

Table 3. Summary of plutonium processes at W. R. Grace. 

Timeframe Customer Product kg Pu U (Mass) Pu (Mass) U 

Enrichment

1965-1966a DuPont/SROO MOX fuel rods 16 99.7% ~0.315% Depleted

1967-1971a SEFOR/GE/AEC

MOX; 2,000 fuel 

rods and scrap 

dissolution

746 80.0% 20.0% Depleted

1972b

Halden/NFSResearch Facilities 

Design (RFD) 

MOX fuel rods 3 98.5% to 

97.5% 

1.5% to 

2.5% 

Depleted and

1.0% to 5.0%

1972-1973b

Big Rock Point 

(Consumers)/NFSRFD

MOX fuel 

assemblies 47 97.73% Average

2.27% 

Average

2.41%

Total Not applicable Not applicable 812.0 Not 

applicable

Not 

applicable

Not 

applicable

Sources: NFS 1988; 1989a, PDF p. 119. 

a. AEC Programs (16 kg + 746 kg = 762 kg, which is 94% of the total plutonium processed).

b. NFS Programs (3 kg + 47 kg = 50 kg, which is 6% of the total plutonium processed).

The plutonium facilities at W. R. Grace were involved with the dissolution of plutonium metal 

and oxide; coprecipitation of uranium-plutonium; wet or dry blending of MOX powders; pellet 

production and inspection; rod loading, welding, and inspection; scrap dissolution (for which 

NFS added facilities in the late 1960s); and full laboratory service (NFS 1988). 

Building 110 plutonium areas included: Area C (Wet Lab Chemistry) and Area D 

(Spectrographic Lab). Building 234 plutonium areas were: Area A (Batch Weigh), Area B 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 9 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

(Former 233U Process), Area C (Pelleting), Area D (Fabrication), Area E (Lab), Area F (Office), 

Area G (Clean Change), Area H (Process Change), Area I (Material Unloading), Area M (Air 

Lock), Areas 67 and 68 (Condensate Stations), and the Wet Cell area (NFS 1988). 

Equipment in the facilities was located primarily in gloveboxes or in a single limited-entry cell 

adjacent to the conversion area. In addition to gloveboxes, the plutonium plant contained 

equipment such as metal tanks; glass columns; pumps; mixing vessels; blenders; drying, 

conversion, and sintering furnaces; pellet press, cut-off machine and centerless grinder; 

outgassing equipment; inspection jigs; welders; leak test gear; liquid and air high-efficiency

particulate filters; miscellaneous laboratory equipment; ventilation fans; wet scrubbers; and 

piping (NFS 1988). 

The SEFOR project processed the greatest majority of the MOX fuel rods and scrap dissolution 

at W. R. Grace. This project also had the largest percentage of plutonium in its MOX. It is 

favorable to claimants to assume the SEFOR MOX as a default assumption. 

The AEC projects account for 94% of the plutonium fuel W. R. Grace produced. Of that, the 

SEFOR project accounted for 98%, with the DuPont/SROO project accounting for the other 2%. 

No information is available on the MOX fuel produced for DuPont/SROO. The composition of 

the plutonium used in the SEFOR project was used for determination of the composition of the 

various plutonium radionuclides. The original order for SEFOR plutonium was prepared as 

plutonium nitrate solution by the Atlantic Richfield Hanford Company between November 1965 

and December 1966. This nitrate solution was then shipped to NFS where the plutonium nitrate 

solution was blended with depleted uranium nitrate solution. The original order for plutonium 

from Hanford totaled 545 kg plutonium (Higinbotham 1994, PDF pp.32-33). Details of date of 

separation and preparation of the remaining source material are unknown. 

NFS (1988, PDF p.10) provides an isotopic composition of the SEFOR project material type 

adjusted for radioactive decay for 1970 and 1988. The SEFOR material is also identified by a 

240Pu assay of ~8.3% and a Pu:U ratio of 1:4 (NFS 1989b, PDF p. 107). The SEFOR mixture is 

the default plutonium assumption, as shown in Table 4. The year of separation was selected at a 

time without americium activity. This resulted in an estimate that the 1970 material was aged 

14.313 years. These assumptions were used to complete the remainder of Table 4. The resulting

238Pu value is not identical to that specified in NFS 1988 (0.036%). The 238Pu value is adjusted 

to increase the wt % sum to 100. 

The SEFOR MOX is also assumed during the time of the DuPont/Savannah River project (which 

occurred before the SEFOR project), as the DuPont/Savannah River source material is unknown. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 10 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 4. Default plutonium assumptions, SEFOR MOX. 

Material Age 238Pu 

(wt %)

239/240Pu 

(wt %)

241Pu 

(wt %)

242Pu 

(wt %)

241Am 

(wt %)

Depleted U

(wt %)

Fresh (2 Weeks) 0.050 98.948 0.948 0.052 0.002 400

5 Year 0.048 98.951 0.747 0.052 0.202 400

10 Year 0.047 98.955 0.587 0.052 0.360 400

20 Year 0.043 98.965 0.363 0.052 0.577 400

Source: NFS 1988, PDF p.10.

Note: For Material Age, 1970 is assumed to be representative of 14.313-year-aged material. Therefore, because the 

production of the plutonium nitrate solution for use at the W. R. Grace site occurred around the 1965 to 1966 

timeframe (Higinbotham 1994), the fresh and 5-year-aged ratios are not applicable to W. R. Grace. Therefore, 

the 10-year-aged ratios were applied from 1965 through 1974, and the 20-year-aged ratios were applied to all 

intakes starting in 1975.

BIOASSAY DATA

NIOSH does not have a database of bioassay data from the site, but the NIOSH-Division of 

Compensation Analysis Claims Tracking System (NOCTS) has a sufficient number of claims 

with plutonium bioassay data to perform a coworker intake analysis for the period of plutonium 

production at W. R. Grace from 1967 to 1973. The derived intake rates for 1967 were extended 

back to include January 1, 1965, through 1966, when plutonium startup operations began (NFS 

1988). 

Although some plutonium bioassay data are available for other years, they are insufficient for the 

statistical analysis needed for a coworker study. Average alpha airborne concentration data from 

1976 through 1993 was used to develop intake rates for plutonium; these data are from routine 

general area air sampling in the plutonium facilities. These intake rates are applicable for 

workers entering the building for various reasons, but are not applicable for D&D activities or 

other work that might have disturbed contamination. For the period between the end of the 

coworker data in 1973 and the beginning of the airborne concentration data in 1976, guidance in 

ORAUT-OTIB-0070, Dose Reconstruction during Residual Radioactivity Periods at Atomic 

Weapons Employer Facilities (ORAUT 2012), was used to connect the intake rates between the 

two periods, using an exponential decay curve. The intake rates developed from the airborne 

concentration data ending in 1993 were then extended from 1994 through March 1, 2011. 

One of the MOX Fuel Fabrication Facilities Decommissioning Project objectives was to restore 

the existing facilities and site to levels of contamination which would permit “unrestricted” use. 

In November 1992, the project work scope was modified to include the removal of significantly 

more uranium and plutonium material in contaminated soil beneath Area B of Building 234 than 

was originally envisioned. Area B, the Wet Chemistry Cell area, was used for nitric acid 

dissolution and mixing of plutonium and depleted or low-enriched uranium. Much of the soil 

was excavated from under the Wet Cell for several months in 1993 and packaged as TRU waste. 

However, some soil contaminated with plutonium and uranium at TRU levels remained beneath 

the Wet Cell area and in a cell below ground (NFS 2009), and removal was planned to be 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 11 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

conducted as part of plantwide decommissioning efforts (NFS 1994). Because contamination 

still exists, it follows that the derived intake rates ending in 1993 should be extended from 1994 

through March 1, 2011. 

COWORKER INTAKE RATES BASED ON BIOASSAY (1965-1973) 

Attachment A, Plutonium Coworker Statistical Analysis, provides the detailed method and 

statistical analysis for the development of the plutonium coworker intake rates based on NOCTS 

data. Attachment B, Plutonium Coworker Statistical Analysis Instructions, provides the 

instructions for the analysis for the development of the plutonium coworker intake rates. 

The recommended coworker intake rates are shown in Tables 5 and 6. Table 5 summarizes the 

plutonium intake rates that correspond to an intake of Type M materials. Table 6 summarizes 

the plutonium intake rates that correspond to an intake of Type S materials. Dose from

plutonium Type Super S materials will be estimated according to the methods described in 

ORAUT-OTIB-0049, Technical Information Bulletin: Estimating Doses for Plutonium Strongly 

Retained in the Lung (ORAUT 2010). 

Table 5. Plutonium intake rates based on bioassay (Type M) (dpm/d).

Start End 50th Percentile GSD 95th Percentile

01/01/1965 12/31/1968 49.93 4.65 626.64

01/01/1969 12/31/1971 10.96 3.39 81.50

01/01/1972 12/31/1973 2.567 6.59 57.10

Note: A SEFOR PuO2-UO2 MOX should be assumed.

Table 6. Plutonium intake rates based on bioassay (Type S) (dpm/d). 

Start End 50th Percentile GSD 95th Percentile

01/01/1965 12/31/1968 1,692 5.07 24,431

01/01/1969 12/31/1971 291.9 3.30 2,076

01/01/1972 12/31/1973 107.2 6.59 2,384

Note: A SEFOR PuO2-UO2 MOX should be assumed.

Plutonium coworker intakes should be assigned to workers who were not monitored via 

bioassay, or to fill in gaps in monitoring data, as specified in ORAUT-OTIB-0060, Internal Dose 

Reconstruction (ORAUT 2018a). Plutonium workers with a hands-on operations job categories

should be assigned the 95th-percentile coworker intake rates as a constant distribution. 

Radiological support workers should be assigned the coworker intake rate geometric mean (GM) 

as a lognormal distribution with a geometric standard deviation (GSD). Supervisors should be 

assigned 50% of the radiological support worker intake rates assuming the same lognormal 

distribution and GSD. Administrative workers should be assigned 10% of supervisor intake rates 

assuming the same lognormal distribution and GSD.
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 12 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

EXPOSURE MODEL TO DEVELOP PLUTONIUM INTAKE RATES BASED ON 

AIRBORNE CONCENTRATION DATA (1976-1993) 

Attachment C, Exposure Model to Develop Plutonium Intakes based on Airborne Concentration 

Data, provides the detailed method used to develop the plutonium intakes based on airborne 

concentration data.

Table 7 summarizes the recommended total gross alpha inhalation and ingestion intake rates. 

The material type (M, S, Super S) that is most favorable to the claimant should be assigned.

Table 7. Total alpha intake rates based on airborne concentration data (dpm/d).

Start End Inhalation 

95th Percentile

Ingestion 

95th Percentile

01/01/1976 12/31/1987 8.74 1.75

01/01/1988 12/31/1993 1.13 0.23

01/01/1994 03/01/2011 1.13 0.23

Although the airborne concentration data are actually reporting total alpha, treating them as total 

plutonium simplifies the calculations and results in an assessment favorable to the claimant. A 

SEFOR PuO2-UO2 MOX should be assumed. Ingestion intakes should also be assigned when 

airborne concentration data are used to assign inhalation intakes as described in OCAS-TIB-009, 

Estimation of Ingestion Intakes (NIOSH 2004). 

For the post-plutonium production period, workers presumed to have exposure in plutonium 

buildings should be assigned the 95th percentile intake rates as a constant distribution. In 

addition, workers with plutonium bioassay data should be assigned intakes based on their data. 

All other workers who are not assumed to have been working in the plutonium buildings should 

receive only environmental intakes. 

D&D workers should be evaluated for intakes of plutonium based on their bioassay 

measurements. 

ORAUT-OTIB-0070 METHOD TO DEVELOP PLUTONIUM INTAKE RATES 

(1974-1975) 

For the gap between the end of the coworker data in 1973 and the start of the airborne 

concentration data in 1976, guidance in ORAUT (2012) was used to derive exposure rates for 

1974 and 1975 using an exponential decay curve fit between the intake rates in 1973 and 1976. 

A decay correction rate was calculated between the midpoint of the 1973 derived coworker 

intake rates for plutonium Types S and M as Year 1 and the midpoint of the 1976 intake rates 

derived from airborne concentration data. This was done for the 50th and 95th percentiles. The 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 13 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

higher of the two GSDs was applied to be favorable to the claimant. However, it is favorable to 

the claimant to assume the 95th percentile intake rates. 

Though the airborne concentration data are reporting total alpha, treating them as total plutonium

simplifies the calculations and results in an assessment favorable to the claimant. 

Table 8 summarizes the plutonium intake rates that correspond to an intake of Type M materials. 

Table 9 summarizes the plutonium intake rates that correspond to an intake of Type S materials. 

Table 8. Plutonium intake rates (Type M) (dpm/d).

Start End Inhalation 95th

Percentile

Ingestion 95th

Percentile

01/01/1973 12/31/1973 57.1 11.4

01/01/1974 12/31/1974 30.6 6.11

01/01/1975 12/31/1975 16.4 3.27

01/01/1976 12/31/1976 8.74 1.75

Note: Super S intake rates are assumed to be equal to Type S.

Note: A SEFOR PuO2-UO2 MOX should be assumed.

During the post-plutonium production period, workers presumed to have exposure in plutonium 

buildings will be assigned the 95th percentile intake rates as a constant distribution. All other 

workers that are not assumed to be working in the plutonium buildings will receive 

environmental intakes. 

Table 9. Plutonium intake rates (Type S) (dpm/d). 

Start End Inhalation 95th 

Percentile

Ingestion 95th 

Percentile

01/01/1973 12/31/1973 2384.0 476.8

01/01/1974 12/31/1974 367.9 73.6

01/01/1975 12/31/1975 56.8 11.4

01/01/1976 12/31/1976 8.74 1.75

Note: Super S intake rates are assumed to be equal to Type S.

Note: A SEFOR PuO2-UO2 MOX should be assumed.
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 14 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

REFERENCES

Author unknown, 1988, In vivo Cross Comparison Study, Erwin, Tennessee, September 21. 

[SRDB Ref ID: 41262, PDF pp. 25-51] 

Congress (U.S. Congress), 1986, Erwin Nuclear Fuel Services—Hearing Before the 

Subcommittee on Energy Conservation and Power of the Committee on Energy and Commerce 

House of Representatives, Ninety-Ninth Congress, Second Session, September 18, 1986, Serial 

No. 99-178, Washington, D.C. [SRDB Ref ID: 18808]

DOE (U.S. Department of Energy), 2017, W. R. Grace (Tennessee), Office of Environmental 

Health, Safety and Security, Washington, D.C., March 28. [SRDB Ref ID: 166041]

EG&G Idaho, 1994, Evaluation of Department of Energy-Held Potential Greater-Than Class C 

Low-Level Radioactive Waste, Idaho Falls, Idaho, September. [SRDB Ref ID: 40398]

Haskins, Archer A., 1995, “Decontamination and Decommissioning of a Uranium Oxide and 

Plutonium Oxide Fuel Fabrication Facility,” Transactions of the American Nuclear Society, 

volume 72, pp. 19-20. [SRDB Ref ID: 36182]

Higinbotham, William, 1994, Material Unaccounted for at the Southwest Experimental Fast 

Oxide Reactor; The SEFOR MUF, Brookhaven National Lab (BNL), Upton, Long Island, New 

York, November 7. [SRDB Ref ID: 150234]

NFS (Nuclear Fuel Services), ca. 1979, Radiation Exposure Summary, 1977-1979, Erwin, 

Tennessee. [SRDB Ref ID: 19315]

NFS (Nuclear Fuel Services), 1988, Decommissioning Project Plan Plutonium Facilities, Erwin, 

Tennessee, October 24. [SRDB Ref ID: 166201]

NFS (Nuclear Fuel Services), 1989a, Memorandums and Correspondence on NFS PlutoniumUranium Scrap, Erwin, Tennessee. [SRDB Ref ID: 109631] 

NFS (Nuclear Fuel Services), 1989b, Plutonium Facilities, Decommissioning Project Plan, 

Condition Addendum, Erwin, Tennessee, April 28. [SRDB Ref ID: 28218, PDF pp. 151-179]

NFS (Nuclear Fuel Services), ca. 1989, Radiation Exposure Summary, 1980-1989, Erwin, 

Tennessee. [SRDB Ref ID: 19316]

NFS (Nuclear Fuel Services), 1991, Preparation of Building 110 for Final Release Procedure, 

Erwin, Tennessee, November. [SRDB Ref ID: 150818]

NFS (Nuclear Fuel Services), 1994, Status of Former Mixed Oxide Fuel Fabrication Facilities at 

Nuclear Fuel Services’ Erwin, TN Site, Erwin, Tennessee, January 10. [SRDB Ref ID: 150815]
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 15 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

NFS (Nuclear Fuel Services), ca. 1999, Radiation Exposure Summary, 1990-1999, Erwin, 

Tennessee. [SRDB Ref ID: 19317]

NFS (Nuclear Fuel Services), ca. 2000, NFS Timeline, Erwin, Tennessee. [SRDB Ref ID: 

18804]

NFS (Nuclear Fuel Services), ca. 2005, Radiation Exposure Summary, 2000-2005, Erwin, 

Tennessee, September 28. [SRDB Ref ID: 19318]

NFS (Nuclear Fuel Services), 2009, Nuclear Fuel Services Frequently Asked Questions for a 

Public Meeting, Erwin, Tennessee, October 29. [SRDB Ref ID: 93259]

NFS (Nuclear Fuel Services) and EkoTec, Inc., 1990, Decontamination & Decommissioning of a 

Plutonium Fabrication Facility, Erwin, Tennessee. [SRDB Ref ID: 165837]

NIOSH (National Institute for Occupational Safety and Health), 2004, Estimation of Ingestion 

Intakes, OCAS-TIB-009, Rev. 0, Office of Compensation Analysis and Support, Cincinnati, 

Ohio, April 13. [SRDB Ref ID: 22397]

NRC (U.S. Nuclear Regulatory Commission), 1991, Environmental Assessment for Renewal of 

Special Nuclear Material License No. SNM-124, Nuclear Fuel Services, Inc., Erwin, Plant, 

Docket No. 70-143, Office of Nuclear Material Safety and Safeguards, Washington, D.C., 

August. [SRDB Ref ID: 36166]

ORAUT (Oak Ridge Associated Universities Team), 2004, Coworker Data Exposure Profile 

Development, ORAUT-PLAN-0014, Rev. 00, Oak Ridge, Tennessee, November 24. [SRDB Ref

ID: 166559]

ORAUT (Oak Ridge Associated Universities Team), 2005, Analysis of Coworker Bioassay Data 

for Internal Dose Assignment, ORAUT-OTIB-0019, Rev. 01, Oak Ridge, Tennessee, October 7. 

[SRDB Ref ID: 19438]

ORAUT (Oak Ridge Associated Universities Team), 2010, Estimating Doses for Plutonium 

Strongly Retained in the Lung, ORAUT-OTIB-0049, Rev. 01 PC-2, Oak Ridge, Tennessee, 

November 29. [SRDB Ref ID: 90666]

ORAUT (Oak Ridge Associated Universities Team), 2011, An Exposure Matrix for W. R. Grace 

and Company in Erwin, Tennessee, ORAUT-TKBS-0043, Rev. 02, Oak Ridge, Tennessee, 

September 16. [SRDB Ref ID: 101734]

ORAUT (Oak Ridge Associated Universities Team), 2012, Dose Reconstruction during Residual 

Radioactivity Periods at Atomic Weapons Employer Facilities, ORAUT-OTIB-0070, Rev. 01, 

Oak Ridge, Tennessee, March 5. [SRDB Ref ID: 108851]
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 16 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

ORAUT (Oak Ridge Associated Universities Team), 2014, Analysis of Stratified Coworker 

Datasets, ORAUT-RPRT-0053, Rev. 02, Oak Ridge, Tennessee, October 8. [SRDB Ref ID: 

136245]

ORAUT (Oak Ridge Associated Universities Team), 2016, Use of Claimant Datasets for 

Coworker Modeling, ORAUT-OTIB-0075, Rev. 01, Oak Ridge, Tennessee, June 17. [SRDB 

Ref ID: 157060]

ORAUT (Oak Ridge Associated Universities Team), 2017a, W. R. Grace Plutonium Coworker 

Support Calculations, Updated Pu Sort Excel Spreadsheet, Oak Ridge, Tennessee, May 31. 

[SRDB Ref ID: 172467]

ORAUT (Oak Ridge Associated Universities Team), 2017b, W. R. Grace Plutonium Coworker 

Support Calculations, Pu Corrections Excel Spreadsheet, Oak Ridge, Tennessee, August 23. 

[SRDB Ref ID: 172466]

ORAUT (Oak Ridge Associated Universities Team), 2018a, Internal Dose Reconstruction,

ORAUT-OTIB-0060, Rev. 02, Oak Ridge, Tennessee, April 20. [SRDB Ref ID: 171554]

ORAUT (Oak Ridge Associated Universities Team), 2018b, Applications of Regression in 

External Dose Reconstruction, ORAUT-RPRT-0087, Rev. 00, Oak Ridge, Tennessee, March 13. 

[SRDB Ref ID: 170100]

SC&A (Sanford Cohen and Associates) and Salient, Inc., 2013, Review of the NIOSH Site Profile 

for the W. R. Grace and Company in Erwin, Tennessee, SCA-TR-SP2013-0041, Rev. 0-Draft, 

Vienna, Virginia, and Jefferson, Maryland, January 16. [SRDB Ref ID: 166040]
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 17 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Attachment A, Plutonium Coworker Statistical Analysis Methods

ORAUT-OTIB-0019, Analysis of Coworker Bioassay Data for Internal Dose Assignment

(ORAUT 2005), describes the general process NIOSH uses to analyze bioassay data for the 

assignment of doses to individuals based on coworker results. ORAUT-PLAN-0014, Coworker 

Data Exposure Profile Development (ORAUT 2004), describes the approach and processes to 

develop reasonable exposure profiles based on available dosimetric information for workers at 

DOE sites. The ORAUT (2004) approach is assumed to be applicable to W. R. Grace, an AWE 

site.

Bioassay Data

Bioassay data in NOCTS for W. R. Grace employees were used to develop a representative 

database of coworker bioassay data using the guidance of ORAUT (2016). Plutonium gross 

alpha (238Pu + 239Pu) urinalysis data were extracted from the NOCTS data for employees at 

W. R. Grace for the period from 1967 through 1973. After extraction, these data were subjected 

to a 100% review for transcription errors and corrected as necessary. The data from one 

employee was excluded beginning in 1972 due to an incident.

The analytical results were converted to units of dpm/day based on an assumed daily urinary 

excretion of 1.4 L/day and the assumption that sample results with no volume noted (i.e., “dpm” 

or “dpm/sample” type) had a volume of 1 L. Results recorded as zero were assumed to be 

censored at 0.03 dpm/L, the decision level noted in the site technical basis document 

(ORAUT 2011). 

Analysis

Statistical analysis of the plutonium gross alpha bioassay data was performed in accordance with 

ORAUT (2005, 2014) using the time-weighted one person-one statistic (TWOPOS) method. 

The data were analyzed on an annual basis except for 1972 and 1973, which were merged due to 

the small amount of data available for each year and the assumption that the exposure potential 

was similar in both years. In 1972, plutonium processing activities were completed (Congress 

1986, PDF p. 72) and the fabrication of fuel elements with a mixture of uranium-plutonium 

MOX was discontinued (NRC 1991, PDF p. 27). Safe shutdown of the MOX facility occurred in 

1973, as previously mentioned.

Table A-1 provides the results of the statistical analysis. 

Intake Modeling

Each result that was used in the intake calculations was assumed to have a normal distribution. 

A uniform absolute error of 1 was applied to all results, thereby assigning the same weight to 

each result. Because of the nature of work at W. R. Grace, intakes could have been chronic or 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 18 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table A-1. 50th and 84th percentile urinary excretion rates of plutonium gross alpha, 1967 to 1973 (dpm/d).

Effective Bioassay 

Date

50th 

Percentile

84th 

Percentile GSD Number of Individuals

07/01/1967 0.183 0.472 2.58 34

07/01/1968 0.118 0.763 6.48 36

07/01/1969 0.065 0.202 3.11 25

07/01/1970 0.033 0.172 5.23 28

07/01/1971 0.032 0.070 2.18 37

01/01/1973 0.007 0.046 6.44 29

acute. However, a series of acute intakes can be approximated as a chronic intake. Therefore, 

intakes were assumed to be chronic and to occur through inhalation with a default breathing rate 

of 1.2 m3/hour and a 5-μm activity median aerodynamic diameter particle size distribution. 

The results were entered in the Integrated Modules for Bioassay Analysis (IMBA) computer 

software to obtain intake rates for the assignment of dose distributions. IMBA was then used to 

fit the bioassay results to a series of chronic inhalation intakes. The intake assumptions were 

based on observed patterns in the bioassay data. Periods with constant chronic intake rates were 

chosen by the selection of periods in which the bioassay results were similar. A new chronic 

intake period was started if the data indicated a significant sustained change in the bioassay 

results. By this method, the years from 1967 through 1973 were divided into multiple chronic 

intake periods. For intake modeling purposes only, the plutonium gross alpha results were 

assumed to be 239Pu. 

The plutonium intake periods were independently fit using only the bioassay results from the 

single intake period. This method likely results in an overestimate of intakes for exposures that 

extend through multiple assumed intake periods. 

The solid lines in Figures A-1 to A-6 (see Attachment A) show the individual fits to the 50th and 

84th percentile excretion rates for Type M materials. Excluded results are shown in red (dark 

gray in grayscale) in the figures; included results are shown in blue (light gray in grayscale). 

Figures A-7 and A-8 show the 50th-and 84th percentile predicted excretion rates, respectively, 

from all Type M intakes. Figures A-9 to A-14 show the 50th-and 84th-percentile predicted 

excretion rates for Type S materials. Figures A-15 and A-16 show the 50th-and 84th-percentile 

predicted excretion rates, respectively, from all Type S intakes.

Intake Assignment

For each intake period below, the GSDs were determined by dividing the 84th-percentile intake 

rates by the 50th-percentile rate. For the calculation of doses to individuals from bioassay data, a 

GSD of three is used to account for biological variation and uncertainty in the models (ORAUT 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 19 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

2014). The same models were used for fitting the coworker data, so the same uncertainty 

applies. Therefore, a minimum GSD of 3 was assigned for each of the intake periods. 

Multiple intake periods were fit to the derived 50th-and 84th-percentile plutonium excretion data. 

The 95th-percentile intake rates were calculated using the following equation: 

 Equation A-1 1 645 - - = × . 95th percentile intake 50th percentile intake GSD

Table A-2 summarizes the 50th-and 95th-percentile plutonium intake rates that correspond to an 

intake of Type M materials that were calculated from the excretion rates. Table A-3 provides the 

same information for Type S materials. 

Table A-2. Type M plutonium gross alpha intake rates (dpm/d).

Start End 50th 

Percentile GSD 95th Percentile

01/01/1967 12/31/1968 49.93 4.65 626.64

01/01/1969 12/31/1971 10.96 3.39 81.50

01/01/1972 12/31/1973 2.567 6.59 57.10

Table A-3. Type S plutonium gross alpha intake rates (dpm/d). 

Start End 50th 

Percentile GSD 95th Percentile

01/01/1967 12/31/1968 1,692 5.07 24,431

01/01/1969 12/31/1971 291.9 3.30 2,076

01/01/1972 12/31/1973 107.2 6.59 2,384
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 20 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Plutonium Statistical Analysis Results

Figure A-1. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1967 to 1968, 

Type M 

Figure A-2. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1969 to 1971, 

Type M 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 21 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-3. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1972 to 1973, 

Type M 

Figure A-4. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1967 to 1968, 

Type M 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 22 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-5. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1969 to 1971, 

Type M 

Figure A-6. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1972 to 1973, 

Type M 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 23 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-7. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, all years, 

Type M 

Figure A-8. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, all years, 

Type M 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 24 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-9. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1967 to 1968, 

Type S. 

Figure A-10. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1969 to 1971, 

Type S. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 25 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-11. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, 1972 to 1973, 

Type S. 

Figure A-12. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1967 to 1968, 

Type S. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 26 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-13. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1969 to 1971, 

Type S. 

Figure A-14. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, 1972 to 1973, 

Type S. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 27 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure A-15. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 50th percentile, all years, 

Type S. 

Figure A-16. Predicted plutonium gross alpha bioassay results calculated using IMBA-derived plutonium 

gross alpha intake rates (line) compared with measured bioassay results (dots), 84th percentile, all years, 

Type S. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 28 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Attachment B, Plutonium Coworker Statistical Analysis Instructions

This attachment provides the instructions used to perform the analysis for the development of the 

plutonium coworker intake rates. 

Data Sources:

• W. R. Grace Plutonium Coworker Support Calculations, Updated Pu Sort Excel Spreadsheet

(ORAUT 2017a). 

• W. R. Grace Plutonium Coworker Support Calculations, Pu Corrections Excel Spreadsheet

(ORAUT 2017b). 

Instructions

• Update the source data file using the source data corrections file and identifying lines by the 

“Unique ID#” column. 

o Replace individual cell contents based on cell contents in the corrections file. 

o If a cell in the corrections file contains “blank,” then delete that cell’s contents in the 

source data file.

o If the corrections file “HP Review Comments” column contains the word “exclude” 

or “remove” then do not use that line for the statistical analysis.

• “Use the Sample Date” column (Column J) as the date of sample collection.

o If the month and/or day of the date are illegible (“XX” characters), substitute in the 

month and/or day most claimant-favorable for the TWOPOS calculation. 

o Do not use results with an illegible year.

• “Use the Claim #” field (Column A) as the individual identifier.

• Only use data with “urine” in Column G.

• Data set exclusions:

o Exclude all data from claim [redacted] beginning in 1972 due to an incident. 

o Exclude data after 12/31/1973. 

• Assume all results are plutonium gross alpha measurements. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 29 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

• Assume records with units of “dpm/sample” or “dpm/s,” and no sample volume, have a 

sample volume of 1 L. 

• Assume records with units of “dpm/l” have a sample volume of 1 L. 

• Assume record with volume units of “ml” have a volume of mL. Convert this volume to L. 

• The sample with “UniqueID#” = 876 has no volume units. Assign it volume units of mL and 

convert the volume to L. 

• Assume any “Result” equal to 0 is censored at 0.03 dpm/L. 

• Divide the “Result” by the volume and multiply by 1.4 L to convert “Result” to activity 

excreted per day.

• Perform the statistical analysis on an annual basis for 1967 through 1973 (except merge 1972 

and 1973) in accordance with the TWOPOS method in the latest revision of ORAUT-RPRT0053 (ORAUT 2014). 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 30 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Attachment C, Exposure Model To Develop Plutonium Intakes Based on Airborne 

Concentration Data

This attachment provides the detailed method used to develop the plutonium intakes based on 

airborne concentration data. 

Methods

Annual or semiannual average airborne concentrations in percent of the maximum permissible 

concentration (MPC) from plutonium facilities were converted to inhalation intake rates in units 

of dpm/day. A lognormal distribution was fit to the annual data using the regression on order 

statistic method (ORAUT 2014, 2018b). The data were analyzed as two periods with a single 

distribution in each period. The first period was 1976 through 1987, and it consists of 84 values. 

The second period is 1988 through 1993, and it consists of 51 values. The reason for analyzing 

the data as two separate periods is due to the trend in the results. From 1976 through 1987, the 

facility was shutdown. From 1988 through 1993, characterization, preparation for D&D, and 

D&D activities occurred. The preparatory work for D&D appears to coincide with the trend of 

lower airborne concentrations beginning in 1988 (NFS 1994, PDF p.7-8). D&D of the MOX 

facility began September 1990.

Airborne Concentration Data

Gross alpha airborne concentration data were obtained from the Site Research Database (SRDB) 

(NFS ca. 1979, ca. 1989, ca. 1999, ca. 2005). These data were assumed to be representative of 

W. R. Grace radiological worker exposure because the data were taken from the plutonium 

buildings at W. R. Grace. Although gross alpha airborne concentration existed at W. R. Grace 

through 2005, there were no data from plutonium buildings beyond 1993. Therefore, this 

exposure model ended in 1993. 

These alpha airborne concentration results were compiled by the Project’s data entry group into a 

spreadsheet that contains average airborne alpha radioactivity concentrations in units of % MPC 

for 1976 to 1993 by building, area, and process. These data were subjected to 100% review for 

transcription errors and corrected, as necessary. A second spreadsheet was developed from the 

previous one for summarizing and further review.

NFS (1988) identified specific areas in Buildings 110 and 234 as plutonium related. The 

plutonium work locations from these facilities were reviewed and verified. The air concentration 

results from these plutonium areas were then selected for development of an exposure model. 

The only exceptions to the plutonium data were the airborne concentration data associated with 

the 234A-Pu Wet Chem Cell and 234 Cell, which were excluded. The air concentration data 

outside the cell areas were used to assess plutonium intakes for unmonitored workers after the 

end of plutonium operations at the site.

Table C-1 was used to define which air concentration results were associated with plutonium.
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 31 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table C-1. Determination of plutonium vs. uranium areas.

Air Sample Identifier Description/Comment Include or Exclude Data

110A, B Uranium areas Exclude all results unless identified 

as plutonium

110C, D Plutonium areas (see 110D-1 exception 

below) Include unless identified as uranium

110D-1 Uranium Spectrographic Lab; NDA Lab 

results through 1st half of 1987

Exclude unless identified as 

plutonium

110C, D Pu, 233U Labs Include

110 Pu areas Any 110 air sample identified as Pu such 

as Pu Wet Chem Lab, Pu Spec Lab Include

110 Pu Wet Chem Lab

110 Pu Spec Lab

Results for 1st half 1989 are not valid Exclude 1st half 1989, otherwise 

include

110 Any 110 samples not identified as Pu Exclude unless identified as 

plutonium

110 Avg Element not specified, but location added 

in 1990 for D&D Include

234A Production area, several locations Include except for “Cell”

234A Cell Wet Cell or any identified as “Cell” Exclude

234B233U Process Area

This was a decommissioned 233U area used 

for other projects; it has results reported 

through 1985

Exclude

234C Various descriptions (Pu Dissolution Area, 

Fabrication Area) Include

234 Building

Location first appeared in 1986 report, 

determined to be the same as the “234A Pu 

production area”

Include

234 All areas (1990-1993) No uranium areas reported during 

decommissioning period Include

Note: A couple locations appear to have had slight name changes, with the same result reported in subsequent 

reporting period. These are readily identifiable. Do not duplicate that data.
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 32 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Analysis 

Average results in % MPC were reported annually (1976) and semiannually (1977-1993) for 

each plutonium sampling location. The results were converted to intake rates in units of 

dpm/day according to the MPC the records indicate was being used for plutonium, which was 

2 × 10-12 μCi/mL, or 4.44 dpm/m3

. 

A breathing rate of 1.2 m3/hour, an 8-hour workday, and 250 days/year exposure were assumed 

for a total of 2,400 m3

/year.

Table C-2 provides a summary of the plutonium air concentration results.

Table C-2. Plutonium gross alpha air concentration results (1976 to 1993).

Year Percent of 

MPC Average

Percent of 

MPC Maximum

Total Number of 

Airborne 

Concentration Results

1976 23.7 46.5 4 

1977 10.3 25.0 8 

1978 19.9 22.5 8 

1979 15.2 21.3 8 

1980 13.8 30.0 8 

1981 12.2 16.9 8 

1982 7.60 10.0 8 

1983 8.07 10.8 8 

1984 21.0 37.0 8 

1985 11.7 17.8 8 

1986 20.7 23.6 4 

1987 7.99 10.8 4 

1988 2.92 5.5 6 

1989 3.00 3.3 3 

1990 0.07 0.29 12

1991 0.16 0.67 12

1992 0.36 2.38 12

1993 0.44 1.08 6 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 33 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Intake Modeling and Assessment

A lognormal distribution was fit to the data using the regression on order statistic method 

(ORAUT 2018b). 

Table C-3 summarizes the 50th-and 95th-percentile plutonium intake rates that correspond to an 

intake that was calculated from the airborne concentration data exposure model. Ingestion 

intakes should also be assigned when airborne concentration data are used to assign inhalation 

intakes, as described in OCAS-TIB-009, Estimation of Ingestion Intakes (NIOSH 2004), and are 

included in the Table C-3. 

Table C-3. 50th--percentile plutonium intake rates (dpm/d).

Start End

Inhalation 

50th

Percentile

Ingestion 

50th 

Percentile

GSD

Inhalation 

95th 

Percentile

Ingestion 

95th 

Percentile

01/01/1976 12/31/1987 3.503 0.701 1.743 8.741 1.748

01/01/1988 12/31/1993 0.040 0.008 7.616 1.132 0.226

The 1993 intakes should be extended from 1994 through 2011. Figures C-1 to C-2 below show 

the observed plutonium air concentration versus the standard normal quantiles. The y-axis is on 

a logarithmic scale, so data that fall on a straight line on this plot are lognormally distributed. 

The line in the plot is the best-fit lognormal model, where the slope of the line is the GSD and 

the y-intercept is the GM. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 34 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure C-1. Observed 1976-1987 fraction of plutonium MPC versus the standard 

normal quantiles (censored data do not appear on the plot)
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 35 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure C-2. Observed 1988-1993 fraction of plutonium MPC versus the standard 

normal quantiles (censored data do not appear on the plot)
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 36 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

Attachment D, Plutonium Bioassay Program Review

This attachment provides a summary of the plutonium bioassay program at W. R. Grace. 

Information was taken from records in the Site Research Database (SRDB) and from worker 

records in NOCTS. It should be noted that the bioassay data from NOCTS discussed in this 

review is not a complete accounting of all workers who were monitored for intakes of plutonium, 

but some conclusions about the bioassay program can be made from those records coupled with 

other information. 

Table 1 shows key dates for plutonium work, including the production period, idle period, and 

several key dates for the D&D project. For purposes of assessing potential exposures, the 

plutonium work was divided into three time periods based on potential for exposure and the 

differences in bioassay requirements at the site. Each of the three periods are discussed below 

Although nearly all personnel were monitored for intakes of uranium during these periods, only 

some workers were monitored for intakes of plutonium. 

1965 through 1973—Plutonium Production Period

Plutonium fuel was produced starting sometime in 1965 and continuing through 1972. Some 

references indicate the production continued into 1973 before the production facilities were shut

down (see Table 3). The presence of routine sampling for some workers extended into 1973, so 

production was assumed in 1973 whether it was actual production or work on closing the facility.

The bioassay data from claimant records indicates some workers were routinely monitored for 

plutonium intakes by urinalysis from April 1967 through the first half of 1973. The bioassay 

dataset from NOCTS used for the coworker analysis includes multiple workers with multiple 

sample data throughout that period. It is not known if all exposures were monitored during that 

period, so coworker intake data is provided for use in dose reconstructions. 

Per the Table 3 timetable of plutonium projects, the coworker intake assessment covers all the 

production periods except the MOX fuel project for DuPont/SROO that used 16 kg of plutonium 

from 1965 through 1966. The coworker intake rates for the 1967 through 1968 period should be 

used for 1965 and 1966 because no other data are available for that period. There is also an 

existing Special Exposure Cohort class for that period that extends through 1970.

Workers with potential plutonium exposures should be assigned intakes based on individual 

bioassay data and/or coworker data (as provided in this paper) for the period from 1965 through 

1973. Furthermore, because all the plutonium projects involved MOX fuel, all workers with 

potential exposure to plutonium should be assigned uranium intakes based on their uranium 

bioassay data. For the period after 1970, when residual uranium intakes would normally apply 

for exposure to weapons-related AEC uranium in other buildings, those intakes should not be 

applied because uranium bioassay should be used to assess intakes. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 37 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

1974 through 1989—Post-Production Period

The intakes for 1976 through 1989 in Table 7 are based on the 95th percentile of the general area 

air sampling data from the monitored plutonium areas. Because there are no data available for 

1974 and 1975, favorable intake rates were modeled assuming a lognormal depletion curve from 

the operational intakes in 1973 to the intakes based on air samples starting in 1976. 

Based on trends in the air sampling data, calculated intakes from that sampling data were 

assessed as two periods, one from 1976 through 1987 and another from 1988 through 1993. The 

intakes from the 1976-1987 period were based on a concentration of 6.0 × 10-13 μCi/mL, or 30% 

of the MPC of plutonium, while the intakes for the 1988-1993 period were based on a 

concentration of 7.8 × 10-14 μCi/mL, or 3.9% of the MPC. The site was using an MPC of 

2 × 10-12 μCi/mL. A bounding intake for workers who have no plutonium bioassay, but might 

have entered the plutonium facilities, is based on continuous exposure at those levels for 

2,000 hours per year. Based on the MPC, this results in an exposure of 600 MPC-hours per year 

for the 1974-1987 period and 78 MPC-hours per year for the 1988-1993 period. 

From 1974 through 1989 the plutonium facility was shut down awaiting D&D. The NOCTS 

data indicate the routine plutonium bioassay program ended in 1973. There are no references or 

data to indicate a routine bioassay program for plutonium from 1974 through 1989. However, 

NOCTS has a few bioassay results for some workers in some of these years. Table D-1 

summarizes the urinalysis data for plutonium in NOCTS from 1974 through 1989. It should be 

noted that some of the records for a particular worker include laboratory reports of plutonium 

bioassay for several other workers, but those numbers are not included in Table D-1 because the 

results for other workers were redacted and the implied number of additional monitored 

personnel cannot be determined with certainty. 

There were a few known activities that occurred in 1974 through 1989. Records of entries in the 

plutonium facilities was found for the following activities:

• A routine air sampling program in multiple locations started in 1976. 

• Some facility maintenance activities occurred.

• A limited D&D project was performed in 1984. 

• Preparation work for the main D&D project was done in 1988 through 1989. 

Available references and NOCTS data and information about the workers who were monitored 

for plutonium during these years were reviewed for pertinent information on plutonium work and 

bioassay during the 1974 through 1989 period. 

No information was found on activities for the latter half of 1973 through 1975. One worker had 

a single positive bioassay result in 1974 (see Table D-1), but no information is available for the 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 38 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table D-1: Plutonium bioassay data in NOCTS 1974 through 1989.

Year Number of Pu 

Bioassay Results Notes

1974 1 One worker was monitored. Results were reported as

[redacted]. 

1975-1977 0 No Pu bioassay results.

1978 6 [Redacted] workers were monitored. Four results were 

reported as 0 dpm/L. Two results were 0.03 dpm/L.

1979 0 No Pu bioassay results.

1980 7 Seven workers were monitored in July and August. All 

reported 0 dpm/L.

1981 2 Two workers were monitored. Results were reported as 

0 dpm/L.

1982-1983 0 No Pu bioassay results.

1984 6 

[Redacted] workers were monitored [redacted] through

[redacted]. Four results were either 0 or less than the 

sample lower limit of detection. The other two samples 

were [redacted] and [redacted]. The [redacted] 

monitored in [redacted]. 

1985 2 [Redacted] monitored. Results were reported as 0 

dpm/L.

1986-1987 0 No Pu bioassay results.

1988-1989 1+ One worker was monitored. Positive sample followed 

by bioassays.

Note: One worker had multiple bioassay results; however, those were results were not included in this table because 

that worker was on a long-term monitoring program and did not enter plutonium areas during the period.

reason for that monitoring. That worker’s employment ended in [redacted], and no additional 

bioassay or information is available. 

The air sampling records indicate a multilocation routine air sampling program throughout the 

site was established by 1976; it included locations in the plutonium facilities (see Appendix C for 

more information). These samples are believed to have been fixed-location routine samples

rather than job-specific data. At a minimum, personnel would have made entries into the 

plutonium areas to set up and maintain the air sampling pumps and to make routine collections of 

the filters. The sample results are sufficient to estimate or bound intakes from those entries into 

the building or for entries for inspections. As noted in Attachment C, in some years air samples 

were collected in the Wet Cell area of Building 234, which was a separately contained cell 

requiring multiple protective clothing and protection. Although the Wet Cell data are not 

included in the analysis in Attachment C, the monitored areas outside of the Wet Cell were 

included. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 39 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

No records were found of other specific maintenance activities other than records of a worker 

who was monitored several times in 1988 and 1989 after working [redacted]. Table D-1 also 

shows plutonium bioassay records in 1978, 1980, and 1981. Of the 15 total results in NOCTS 

for those years, 13 were reported as 0, and the other 2 were reported as 0.03 dpm/L, although the 

sample-specific detection limit is not provided. No information was found for a reason for those 

bioassay data, although intakes can be estimated from the data. 

In addition to the samples and activities discussed above there are also monitoring results from 

1984 and 1985, which were collected for a limited D&D project. NOCTS had six plutonium 

bioassay samples for [redacted] workers in 1984. Two of those are presumed positive, and 

[redacted] had a plutonium bioassay in early 1985. Per the record of the computer-assisted 

telephone interview (CATI) for one of the monitored workers (claim redacted), part of his duties 

was [redacted]. The CATI provided this information on work that was done in 1984-1985: 

While performing decommissioning work in the Plutonium Facility, [redacted].

This information coincides with a reference concerning a limited D&D project to remove 

welding devices and X-ray equipment previously used on plutonium fuel rods. The NRC 

described the work (NRC 1991): 

During 1983 and 1984, NFS began work to decommission the fabrication area 

of Building 234. This area contained welding devices and X-ray equipment 

used to fabricate and inspect plutonium fuel rods. Materials removed during 

this effort were packaged in drums and burial boxes and are currently being 

stored onsite. 

The reference for this information was an NRC document on the status of the site in 1986 that 

was used to brief a Congressional subcommittee. The same report noted that the plutonium 

processing equipment and gloveboxes continued to remain in the building. Although the worker 

interview and NRC document have slightly different dates (one says the project started in 1983 

the other says 1984), the descriptions of the work are similar. NOCTS had no plutonium 

bioassay data from January 1985 until 1988. For part of that period, May 1985 to April 1, 1986, 

the union was on strike (Congress 1986, PDF pp. 12-46). 

Per Table D-1, the plutonium facility was characterized and systems upgraded in 1988 and 1989 

to prepare for the D&D project, including cold testing of the equipment. One claimant in 

NOCTS was monitored in 1988 and 1989, but that was from cleanup work [redacted]. The 

routine air sample data show airborne levels were lower in these years than in the earlier years. 

Starting in 1988 nearly all worker records in NOCTS have routine chest count results that 

provide detection limits for several radionuclides including 241Am and 239Pu. These were 

performed on a germanium detector system that became operational in September 1987 (Author 

unknown 1988). Because it appears all radiological workers had in vivo counts in this era, the 

presence of a chest count is not necessarily an indicator of exposure to plutonium. However, the 

results can be used to estimate a bounding or missed dose to workers exposed to plutonium. 
White Paper Internal Dosimetry Coworker Intake and Exposure 

Model at the W. R. Grace Company, Erwin, Tennessee

March 1, 2019

Page 40 of 40

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

1990 through 1993—Plutonium Facility D&D

Table D-1 shows cold testing of D&D equipment in the plutonium facility in 1990 before the 

September start of the actual D&D work. The project was completed in December 1993 with the 

exception of some subsurface areas inside the Wet Cell that remained under containment; final 

cleanup of that subsurface area was deferred. 

An April 1989 addendum to the NFS NRC license contained requirements for D&D of the 

plutonium facilities that included bioassay requirements. In addition to the routine bioassay 

program, workers participating in the plutonium D&D project were required to have quarterly 

urine and/or fecal bioassay and annual in vivo examinations (NFS 1989b, PDF p. 170).

A review of NOCTS bioassay records indicate a routine bioassay program was initiated for 

several workers in January 1990, and these records indicate a quarterly frequency consistent with 

license modification. In addition, the records contain additional special samples for some 

claimants. In vivo chest counts are provided in this period as well. It appears routine urine 

quarterly plutonium bioassay ended after the D&D project ended in 1993, although annual in 

vivo examinations continued.